1. Field of the Invention
The present invention relates to a vehicle driving assist system for assisting driver operations.
2. Description of the Related Art
In recent years, vehicles are equipped with various types of control devices for enhancing safety. Such various types of control devices include a skid preventing device for preventing skidding by applying a braking force to a specific wheel when the vehicle behavior becomes unstable, and a traction control device that minimizes excessive slipping of the drive wheels. Generally, when the control is activated, these control devices bring the activation to the driver's attention by turning on an alarm lamp or letting out a warning sound.
For example, Japanese Unexamined Patent Application Publication No. 2006-256456 discloses a vehicle driving-force distribution control device for controlling the driving-force distribution among front and rear wheels of a vehicle. In this device, a steering operation amount by the driver is detected, and a limit determination value of the steering operation-amount is set in a range close to a cornering-force limit based on a skid angle of the front wheels. When the steering operation amount exceeds the limit determination value, the driving-force distribution to the steering wheels is reduced in a stepwise manner so as to assist driver's operations.
However, with the technology which assists driver's operation at the time of activation of the device, as in the aforementioned skid preventing device and traction control device, the assisting process is implemented after the vehicle has already become unstable. Therefore, this assisting function for the safety of the driver does not sufficiently exhibit its effect. On the other hand, in the technology disclosed in Japanese Unexamined Patent Application Publication No. 2006-256456 where the assisting process starts upon comparison with a determination value, the timing for starting the assisting process may unfavorably change depending on how the determination value is set. In addition, there may be a case where the assisting process starts suddenly even though the condition that should have been assisted continuously to the driver was already expected to occur, giving the driver a sense of discomfort.